wince updategram 插入sql数据库 中文是乱码

首先 urlparam = "ph=" + HttpUtility.UrlDecode(中文参数,Encoding.UTF8)
   tring url = "服务器域名/ope/ope?" + urlparam;
   ds.ReadXml(url);

ope.xml 如下
<?xml version="1.0" encoding="GB2312"?>
<ROOT xmlns:updg="urn:schemas-microsoft-com:xml-updategram">
<updg:header>
   <updg:param name="ph" />
</updg:header>
<updg:sync >
   <updg:before>
   </updg:before>
   <updg:after>
   <表名 ph="$ph"/>  
   </updg:after>
</updg:sync>
</ROOT>

参数是中文的 插入数据库就是乱码 哪里出问题了 高手 help

补充：移动开发 ,  Windows Phone